Circuit breaker



y 8 1956 L. L. BAIRD 2,744,974

CIRCUIT BREAKER Filed Aug. 3, 195

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United States Patent CIRCUIT BREAKER Leslie L. Baird, Secane, Pa., assignor to General Electric Company, a corporation of New York Application August 3, 1953, Serial No. 372,079

4 Claims. (Cl. ZOO-50) This invention relates to current responsively tripped circuit breakers and, more particularly, to circuit breakers of the type which, in response to overloads above a predetermined value, are instantaneously tripped by electromagnetic means and, in response to persistent overloads of a lesser magnitude, are tripped after a time delay by thermally-responsive means.

Where a circuit breaker of the above type is disconnectably mounted on a panel board, it is desirable, for safety purposes, that the electrical circuit through the breaker always be interrupted or established by the main contacts of the breaker rather than by the contacts of the disconnect mounting. To meet this safety requirement, it is necessary that the main contacts of the breaker be open whenever the disconnect mounting is disconnected.

It is an object of this invention to provide a new and improved trip device for disconnectably mounted circuit breakers which insures that the main contacts of the breaker are always open at the time when the contacts of the disconnect mounting are opened.

It is a further object of this invention to provide for a circuit breaker a new and improved trip device which may be selectively actuated not only by electromagnetic means and by thermally-responsive means but also by interlock means responsive to disconnection of the circuit breaker from its support.

It is a further object of this invention to provide in a disconnectably mounted circuit breaker having releasable structure for retaining the breaker against a panel board, a simple and dependable interlock linkage which coacts in a novel manner with the releasable retaining structure whereby to insure that the breaker is always open when the circuit breaker is disconnected.

In carrying out my invention in one form, I provide, in a circuit breaker disconnectably retained through disconnect contacts in an electrical circuit by releasable structure, an interlock means operatively interconnected between the releasable structure and the trip device of the circuit breaker in a novel manner which insures that the breaker is in tripped open condition whenever the releasable structure is suflicienfiy released to allow disconnection of the breaker through opening of the disconnect contacts.

The invention will be better understood by considering the folowing description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Figure l is a cross-sectional view through the housing of a circuit breaker embodying the present invention, the contacts and operating mechanism of the circuit breaker being shown in the open or reset position. Figure 2 is a similar view showing the contacts and circuit breaker operating mechanism when the contacts are closed. Figure 3 is a view of the operating mechanism showing the parts in tripped position and with portions of the mechanism being broken away for clarity. Figure 4 is a crosssectional view taken along the line 44 of Fig. 1. Figure 5 is an end view of the trip unit with portions "ice being broken away to show the details of the mechanism. Figure 6 is a sectional view taken along the line 6-6 of Figure 5. Figure 7 is a sectional view taken along the line 7-7 of Figure 5 showing the parts of the trip unit in latched position. Figure 8 is a view taken along the line 7-7 of Fig. 5 but showing the parts in tripped position. Figure 9 is an enlarged detail view of an armature of the trip unit.

Referring to the drawings and particularly to Figures 1 and 6, there is shown a base 1 of molded insulating material on which is mounted a circuit breaker comprising a plurality of pairs of contacts, one pair of which is shown at 2, 3, a common operating mechanism 4 for all of the contacts, and a trip unit 5, which may be actuated to trip the operating mechanism 4 thereby to open the contacts. A cover In of molded insulating material is detachably secured to the base 1 and cooperates therewith to form an enclosure for the breaker assembly.

Referring to Fig. 6, the base 1 is adapted to be mounted against a switchboard panel 6 having extending therefrom a plurality of conducting studs, one of which is shown at 7. The terminals of the circuit breaker comprise disconnecting contact elements cooperating with the studs 7 to form disconnecting devices for establishing an electrical circuit through the circuit breaker. One of these terminals 8 is shown in Fig. 6, by way of example, as including a resilient socket 9 formed of conducting elements 10 resiliently biased radially inwardly by suitable spring means 10a to embrace the stud 7 and thereby electrically interconnect the stud 7 with the circuit breaker. To mechanically mount and retain the base 1 on the panel board 6, there are provided a plurality of releasable clamping elements or screws 11 (only one being shown). Each of the screws 11 extends through an aperture in the base 1 and is threaded into a portion of the panel board 6, so that when the screws are tightened into the position of Figure 6, the base 1 is clamped against the panel board 6.

Referring now to Fig. 1, it is to be understood that, although only one pair of contacts 2, 3 is shown in this figure, the circuit breaker illustrated has a plurality of pairs of relatively movable contacts, such as one pair for each pole of the breaker. As indicated at Fig. 5, a threepole breaker is illustrated. The three pairs of relatively movable contacts are interconnected for simultaneous movement by an insulating tie bar 12, and the movable contact of each pair is adapted to cooperate with a fixed contact which corresponds to the fixed contact 3. The electrical circuits for each of the poles of the breaker are substantially the same. Beginning with conductor 3a, which is connected to one of the breaker terminals, current will flow successively through fixed contact 3, movable contact 2, flexible conductor 12a, interconnected conducting strips 13, through the trip unit 5, and thence to the other terminal 8.

Although there is shown in the drawings a twin-toggle type of operating mechanism 4, as will be described in greater detail hereinafter, it will be apparent that other forms of operating mechanisms may be used with the present invention. In Fig. l the contacts 2, 3 and the cooperating mechanism 4 are shown in the open or reset position. In this reset position a latch piece 16 forming a part of the trip unit 5 is latched in place behind the link 17 of the closing toggle comprising links 17, 18 and 19. In the position of Fig. l the latch piece 16, through its engagement with the link 17, which is pivotally mounted about a fixed pivot 37, is adapted to support the toggle 17, 18, 19 so that the circuit breaker may be closed.

Closing operation of the circuit breaker from the position of Fig. 1 into the position of Fig. 2 may be etfected by manually pivoting the handle 20 in a clockwise direction about the fixed pivot 21. As will be seen in greater detail hereinafter, this pivotal movement of the handle 20 operates to straighten out or expand the links of toggle 17, 18, 19 against the bias of spring 22 into the position of Fig. 2. This expansive movement of the toggle 17, 18, 19 is transmitted through movable pivot 23 to the arm 24 of the moving contact 2 in such a manner that arm 24 pivots in a clockwise direction about its fixed mounting pivot 21 thereby to close contact 2, as shown in Fig. 2. This closing operation, although initiated by handle 24 is actually effected by an operating toggle mechanism comprising a pair of operating links 25, 26 which respectively pivot on parts 21 and 27. The inner ends of these operating links 25 and 26 are joined by a toggle knee pin 28. This knee pin 28 is fixed in link 25 and is loosely received in a registering opening in link 26. Compression springs 31 are carried by link 26 and each bears at one end against part 27, which actually is a cross beam slidably carried in a longitudinally-extending closed-end slot 29 formed in link 26, and bears at its other end against knee pin 28. When the handle 21 is pivoted in a clockwise direction about pivot 21 of Fig. 1 to close the breaker contacts, the knee pin 28 is engaged in a slot 31 formed in the handle. This slot 31 permits a limited independent motion of the handle 20 and the links 25 and 26, so that after the handle 20 moves pin 28 through dead center, the springs 30, which have been compressed by movement up to dead center, rapidly expand to snap the pin 28 into a position at the terminal portion 32 of the slot 31 and slot 29 without restraint from the handle. This rapid snap action of pin 28 is transmitted to the closing toggle 17, 18, 19 through the slotted connecting link 33, which pivotally engages the knee pin 34 of the closing toggle 17, 18, 19 thereby to rapidly expand this toggle 17, 18, 19, so as to rotate contact 2 in clockwise, closing direction about pivot 21 to the position shown in Fig. 2. In this position of Fig. 2, the springs 30 are restrained from further lengthening by part 27 having reached the bottom end 29a of the slot 29 in link 26. So limiting the expansion of springs 30 makes it possible for the handle 20 to assume an indicating position, as will be described hereinafter.

The contacts 2, 3 of the circuit breaker may be tripped open from the position of Fig. 2 into the position of Fig. 3 in the following manner. The latch piece 16 is so inclined at its toggle engaging end 35 that as soon as its opposite end is unlatched or freed by the trip unit 5, in a manner to be described in greater detail hereinafter, the latch piece will instantly be rotated in a counterclockwise direction about pivot 36. This movement is due to the force exerted by opening spring 22 acting to collapse the toggle 17 18, 19 and thus move the link 17 counterclockwise about its fixed pivot pin 37. This action, of course, also collapses the closing toggle 17, 18, 19, which in turn rapidly opens the breaker contacts.

As the above tripping-open action occurs, the carrier 38, which normally supports the cross beam 27, drops, or rotates counterclockwise, about its fixed pivot 39 under the influence of a torsion spring 42 bearing against the handle 20. This dropping action of carrier 38 is per mitted when the closing link 17 is moved into its collapsed position of Fig. 3 because a pin 40 fixed to the outer end of carrier 38 is freed from a supporting cam surface 41 formed on link 17. This dropping action of carrier 38 into the position of Fig. 3 allows the operating assembly 25, 26, 30 to become slack, so that torsion spring 42 bearing against the handle 20 can rotate the handle to an indicating position, where it is shown in Fig. 3. This indicating position of the handle indicates to the operator that the breaker has been tripped.

To reset the breaker from the position of Fig. 3 t the position of Fig. 1, there is provided a part 43 pivoted on fixed pin 39. This part 43 includes an arm 44 adapted to engage under the carrier 38 and lift the carrier into a position in which the toggle link 17 is free to be rotated clockwise about its pivot 37 under the bias of a torsion spring 45, so that cam surface 41 can fall into place under pin 40. This pivotal lifting motion of the part 43 is effected merely by manually rotating the handle 20 about its pivot 21 from the position of Fig. 3 to the position of Fig. 1. From Fig. 1 it may be seen that this pivotal movement of the handle, due to the engagement between extensions 46 and 47, formed on the handle 20 and part 43, respectively, causes clockwise motion and, hence, the desired lifting action of part 43 and carrier 38. When the mechanism 4 is moved into its reset position of Fig. l, the latch piece 16 under the influence of a spring 75 in the trip unit, falls in behind link 17, where said latch piece is locked by a latch 73 in the trip unit, as will appear more clearly hereinafter. In this position, the latch piece 16 is adapted to support and prevent collapse of the toggle 17, 18, 19 until said latch piece 16 is tripped. The means for effecting tripping of this latch piece 16 will now be described.

Referring now to Figs. 58, the trip unit 5 is a unitary structure assembled on its own base 50, which is of molded insulating material. A cover 51 of similar material cooperates with the base 50 to form an enclosure for the trip mechanism assembled on the base 50. This cover 51 may be held in place by screws (not shown) threaded at 49 into supporting structure 56a formed in the base 50. This trip unit 5 is detachably mounted on the base 1 of the circuit breaker by suitable threaded means (not shown) which adapt the trip unit 5 for easy removability and replacement.

The trip unit 5 contains the tripping elements for each of the three poles of the circuit breaker. For each pole of the breaker there is a thermally-responsive trip element 52 and an electromagnetic trip means indicated generally at 53. In a generally known manner, the electromagnetic trip means 53 will be operated substantially instantaneously in response to overloads above a predetermined value, whereas for persistent overloads of a lesser magnitude, the thermally-responsive trip means 52 will operate after a time delay.

The thermally responsive trip element 52 is formed of suitable bimetallic material and is secured at one end, preferably by brazing to conductor 54 which forms the current path through the trip unit for one of the poles of the circuit breaker. At its other end the bimetallic element 52 is adapted to deflect in response to heat variations to eflect tripping of the breaker, as will be described in greater detail hereinafter. The conductor 54, to which the bimetallic element 52 is secured, is bent into a U- shaped form and serves as a heater for the bimetallic element. This heater 54 is suitably secured to the base 50, as by threaded elements 55 and 56.

The electromagnetic trip means 53 comprises a laminated U-shaped magnet 57 partially surrounding conductor 54 and clamped against the back of the base by screws 58. An armature 59, which is pivotally mounted on the base 50 at 60, has one end adapted to be attracted to the magnet 57 in response to a predetermined overcurrent flowing in conductor 54. This pivotal movement causes the other end of the armature 59 to rotate in a clockwise direction about pivot 68 and to effect tripping of the breaker, as will become apparent as the description proceeds.

A common trip bar 64 of molded insulating material extends transversely across the three poles of the trip device 5 and is actuable by any one of the three bimetallic elements 52 or by any one of the three electromagnetic armatures 59. The trip bar 64 is pivotally mounted at 70 on a pair of brackets 71 and is biased in a counterclockwise direction by adjustable tension spring 72. As more clearly shown in Fig. 7, a latch 73, which is suitably secured to the trip bar 64, normally locks in behind an end portion 74 of latch piece 16. The latch 73 is normally held in this locking position by the bias of spring 72, but when the trip bar 64 is rotated in a clockwise direction in response to operative movement of one of the trip means, the latch 73 releases the latch piece 16 for counterclockwise motion about its pivot 36 under the force of the breaker mechanism 4 which collapses due to the removal of support from toggle element 17 by the tripped latch piece 16. This counterclockwise motion of latch piece 16 is against the bias of spring 75, which is adapted to reset the latch piece into the position of Fig. l or Fig; 7 when the operating mechanism is reset by manual operation of the handle 20, as previously described.

More specifically, tripping of the trip bar 64 by the bimetallic element 52 is effected through a screw '76 mounted on the end of the bimetallic element by a self locking nut 77 welded to the bimetallic element. When the bimetallic element 52 is sufliciently deflected in response to temperature variations of the heater 54, the attached screw 76 contacts the trip bar 64 and rotates it in a clockwise, tripping direction. Similarly, tripping of the trip bar 64 by the electromagnetic armature is elfected through a screw 78 mounted on the end of armature 59 by means of a nut 79 welded thereto. When the armature 59 is sufiiciently pivoted in response to the attraction of magnet 57, the attached screw 78 contacts the trip bar 64 and effects rotation of the trip bar in a clockwise tripping direction. This pivotal movement of armature 59 is controlled by a calibration spring 80, which is adjustably connected between selected points on the magnet and a screw 80a adjustably connected to an end of the armature 59. By adjusting this spring 80, the current rating for instantaneous tripping (magnetic tripping) may be varied as desired.

Another means for varying the current setting for instantaneous tripping is provided in the form of an adjustable resilient stop 81, against which the upper end of the armature 59 normally rests. This stop is clamped in place by a nut 82 on the outside of the trip unit engaging a threaded part secured to the stop 81. When the nut is loosened, the stop 81 may be moved to change the air gap between the magnet 57 and the armature 59 whereby to change the calibration of the instantaneous feature.

An important feature of this device, and especially the trip unit, is the provision of an interlock means 90 which insures that the breaker contacts 2, 3 are always open before the disconnect contacts 7, 9 have been opened as a result of removal of the circuit breaker base 1 from the panel 6. From a safety point of view, it is quite important that the circuit through the breaker be inter rupted at the contacts 2, 3 rather than at the disconnect contacts 7, 9. The interlock means 90 comprises a linkage including a lever 91 pivoted on the base 1 by pivot pin 92 and biased in a clockwise direction about pivot pin 92 by a leaf spring 93 bearing against the lever 91 and suitably supported on the base 1 by a support portion 94, which is preferably integral with the base 1. In its preferred form, the leaf spring 93 is slotted to receive the supported end of lever 91 and bears against the pin 92, so that pin 92 forms a fulcrum about which the spring may flex. Additionally, the linkage includes a trip rod 95 loosely coupled at the outer end of lever 91 by a notch and slot connection that has sutficient play to allow reciprocal movement of the trip rod 95 in response to the pivotal movement of lever 91. The trip rod 95, which extends through and is guided in an opening in the trip unit base 50, is adapted to contact the trip bar 64 in such a manner as to be capable of causing clockwise, tripping movement of the trip bar 64 under the bias of spring 93. This tripping movement is normally prevented, however, by the engagement between the retaining portion or head 96 of the mounting screw 11 and an extension 97 formed on the lever 91. When the breaker mounting screw 11 is tightened fully, the head 96 through its engagement with extension 97 rotates the lever 91 about pivot 92 in a counterclockwise direction against the bias of spring 93, and as a result, withdraws the trip rod 95 to a sufficient degree to permit the trip bar 64 and latch 73 to be reset. Whenv latch 73 is so reset, it is then adapted to lock the latch piece in the position of Fig. 1 or Fig. 7, wherein said latch piece 16 can support the operating mechanism 4 so that breaker contacts 2, 3 may be closed by manual operation of the handle 25. If the breaker is inadvertently left in the closed position at the time it is desired to effect removal of the circuit breaker supporting base 1 from the panel 6, the necessary loosening of the screw 11 will result in freeing the lever 91 to the extent that the bias of spring 93 acting through parts 91 and 95, will trip open the breaker before it can be removed from its disconnect mounting 7, 9, 10. Thus, it will be seen that the breaker contacts 2, 3 cannot be closed until the mounting screw 11 is tightened, and conversely, the breaker cannot be removed from the panel 6 until the mounting screw 11 is loosened to effect opening of the breaker contacts, as is desired.

It will be observed that the head 96 performs the dual function of (1) retaining the base 1 adjacent the fixed structure 6 so as to prevent disconnection of the disconnect device 9, 10 until the head is withdrawn a predetermined minimum distance from the fixed structure and (2) of controlling the interlock means so that the trip device 5 is actuated before the head is withdrawn said predetermined minimum distance. By utilizing the retaining portion or head 96 of the screw 11 to perform this dual function, there is provided a simple and effective structure which insures accurate operation of the interlock means 90.

It will be apparent from the above description that the trip bar 64 and, correspondingly, the circuit breaker contacts 2, 3, may be selectively actuated not only by electromagnetic means 53 and by thermally-responsive means 52 but also by interlock means 90 in response to disconnection of the circuit breaker from its support 6.

While there has been shown and described a particular embodiment of the invention, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention, and that it is intended by the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, panel structure having an electrical conductor associated therewith, a circuit breaker including a base which is provided with a disconnect device for electrically connecting said circuit breaker to said conductor, releasable structure comprising an element extending outwardly from said panel structure, said element having mounted thereon a retaining portion which retains said base adjacent said panel structure and prevents disconnection of said disconnect device from said conductor until said retaining portion is withdrawn a predetermined minimum distance relative to said panel structure, said circuit breaker comprising relatively movable contacts and a trip device actuable to open said contacts, and interlock means engaging said retaining portion and operatively interconnecting said trip device with said releasable structure, said .interlock means being effective to actuate said trip device in response to movement of said retaining portion a distance less than said predetermined minimum distance.

2. in combination, panel structure having an electrical conductor associated therewith, a circuit breaker having a base provided with a disconnect device cooperating with said conductor for electrically interconnecting said circuit breaker and conductor, releasable structure comprising a threaded element extending outwardly from said panel structure, said threaded element having mounted thereon a retaining portion which retains said base adjacent said panel structure and prevents disconnection of said disconnect device from said conductor until said retaining portion is withdrawn a predetermined minimum distance relative to said panel structure, said circuit breaker comprising relatively movable contacts and a trip device actuable to open said contacts, and interlock means engaging said retaining portion and operatively interconnecting said trip device with said releasable structure, said interlock means being effective to actuate said trip device in response to movement of said retaining portion a distance less than said predetermined minimum distance.

3. In combination, a circuit breaker mounting panel having a first disconnect contact mounted thereon, a circuit breaker including a pair of circuit interrupting contacts and having a base provided with a second disconnect contact cooperable with said first disconnect contact, current responsive tripping means mounted upon said base and including a tripping member movable automatically to effect separation of said interrupting contacts, interlock means biased to move said tripping member to its tripped position, and mounting means detachably securing said base to said panel with said disconnect contacts in engagement, said mounting means including a securing element extending outwardly from said panel and having a retaining portion mounted on said element and retaining said base adjacent said panel, said retaining portion normally engaging said interlock means to restrain its movement when said mounting means is in securing position.

4. In combination, panel structure having an electrical conductor associated therewith, a circuit breaker having a base provided with a disconnect device cooperating with said conductor, releasable structure comprising a threaded element extending outwardly from said panel structure, said threaded element having mounted thereon a retaining portion which retains said base adjacent said panel structure and prevents disconnection of said disconnect device from said conductor until said retaining portion is withdrawn a predetermined minimum distance relative to said panel structure, said circuit breaker comprising relatively movable contacts and a trip device actuable to open said contacts, and interlock means operatively connecting said trip device with said releasable structure, said interlock means comprising a pivotally mounted lever and spring means biasing said lever in a direction to actuate said trip device, the retaining portion of said releasable structure being arranged to engage a portion of said lever so as to oppose said spring means, said interlock means being effective to actuate said trip device in response to movement of said retaining portion a distance less than said predetermined minimum distance.

References Cited in the file of this patent UNITED STATES PATENTS 

